Walmart Heads Fortune 500 List of Top Companies in Big Year For Energy firms

Spin-offs, mergers and the US energy boom changed the face of corporate America last year, according to Fortune magazine's latest poll of top companies.

Walmart reclaimed the top spot in 2012's Fortune 500, which ranks businesses by revenue. The retail giant pushed the oil company Exxon Mobil back into second position after a 5.9% rise in sales, to $443.9bn (£285bn).

Facebook made the Fortune 500 for the first time, in at 482, after going public less than a year ago. The social network site beat a record set by Google for the speed with which it joined the elite list.

Apple was the highest ranked technology company, rising from 17th to sixth position and cracking the top 10 for the first time. Hewlett Packard dropped from 10 to 15 after writing off $16bn on botched acquisitions in 2012.

But energy dominated the top of the poll, with Chevron in the third slot and the refiner Phillips 66 fourth. Phillips 66, once part of ConocoPhillips, was one of three new giants to enter the 500 after a corporate spin-off (when a company splits off a section of itself, declaring that part a separate business).

Kraft Foods, the US grocery business of the Kraft empire, was spun off last October, and took the 151st slot in this year's poll. Its former parent, Mondelez International, kept international brands such as Cadbury and Oreo, and took the 88th slot.

The third spin-off to join the 500 was Huntington Ingalls Industries (ranked 380) one of America's largest military shipmaker. Its parent company, Northrop Grumman (ranked 120), shed Huntington to focus on its core aerospace franchise.

Mergers and acquisitions knocked 13 companies, with combined sales of $201bn, out of the latest poll. Ten of those deals involved another player in the ranking, with energy firms proving the most acquisitive sector.

The financial services sector was last year's biggest winner. It made a total of $200bn in revenues in 2012, $53 bn more than technology, which came in second.